The present invention relates generally to tubular joints for use in prothetic devices. More particularly, the invention relates to a tubular joint for receiving and fastening tube-like skeleton elements of an artificial limb, provided with an adjustable manipulation means for changing an inner diameter of the tubular joint.
Known structures of artificial limbs including tubular skeleton elements have a number of disadvantages. The tubular skeleton elements are usually stably adjustable and cosmetically coated so as to satisfy requirements to artificial limbs.
To connect the tube-like skeleton, element for example to a joint, tubular joints or couplings have been utilized which have been formed with longitudinal slots to receive the ends of respective tubes. A flange portion has been provided at the edge of the longitudinal slot, through which flange a setscrew was extended so that the width of the slot has been changed and adjusted by the setscrew. A decrease in the slot width after the tubular member has been inserted caused a decrease in the inner diameter of the tubular coupling so that the tubular member was clamped in the tubular coupling.
Research which has been conducted with conventional tubular couplings or joints has showed that despite of the fact that conventional couplings could satisfactorily serve for a almost a year they are rather disadvantageous. Since the decrease in the slot width causes a descrease in the inner diameter of the tubular coupling this leads to even further decrease of the inner diameter of the coupling at the free end thereof. Therefore the tube inserted into the coupling will be held substantially at its outermost edge. This will lead to circular sharp loads exerted on the clamped tube which will be loaded by local forces. These loads can cause significant local weakening of the tube after a certain period of time which would affect stability of the tube. This can potentially damage the tube connection, for example a tube connection of the hip joint with the upper shank joint tube, due to a lever ratio and relatively great forces acting on the tube connections. With the use of fiber-reinforced plastics tubes there is a risk of damaging of fiber laminations oriented in the direction of loads exerted on the tubes.